Dual slope A/D converters designed to achieve optimum conversion accuracy have required and have incorporated arrangements for providing offset and drift voltage correction. A representative drift compensated circuit is described in U.S. Pat. No. 3,654,560 issued Apr. 4, 1972 to Cath et al. That patent describes a "rezero" or autozero state during which a feedback loop is closed around a storage capacitor provided for correction purposes. Considerable care is required to properly charge the storage capacitor to an accurate offset level since noise, loop instability, settling time effects, leakage, and capacitor anomalies can all detrimentally affect conversion accuracy.